The invention relates to a hemo(dia)filtration apparatus comprising a blood filter divided by a membrane into two chambers, in which the first chamber is connected into a dialyzer fluid path and the second chamber is connected into a blood path, in which the dialyzer fluid path is a supply line extending from a means for preparing the dialyzer to a blood filter and into which a first balance chamber is connected, and which has a discharge line extending from the blood filter to a drain and into which a second balance chamber is connected, a pump for conveying dialyzer fluid within a closed dialyzer fluid system, a bypass line connecting the supply line with the discharge line of the dialyzer fluid path, in which a bypass valve is arranged, an ultrafiltration device, a first sterile filter incorporated in the supply line between the first balance chamber and the blood filter which is divided by a germ-repelling membrane into a first and a second chamber, and a second sterile filter divided by a germ-repelling membrane into a first and a second chamber.
During hemofiltration blood is conducted past the membrane of a hemofilter, in which part of the serum is withdrawn via the membrane and replaced by a sterile substitution fluid added to the extracorporeal blood path either upstream (predilution) or downstream (post dilution) of the blood filter. In addition, in the hemodiafiltration, the usual hemodialysis is carried out, i.e. dialyzer fluid is conducted past the membrane of the hemodialyzer so that across the membrane an exchange of urophanic substances can take place.
Dialyzer fluid may be produced on-line from fresh water and an electrolyte concentrate and the substitution fluid may be produced on-line from the dialyzer fluid. Though the electrolyte concentrate is as a rule inherently sterile and fresh water is generally germ-free, there is no certainty that the dialyzer fluid produced on-line is absolutely sterile and free of pyrogens, which is why the dialyzer fluid is rendered sterile and pyrogen-free for producing the substitute fluid. To achieve this, dialyzer fluid is removed via a line upstream of the blood filter, into which line at least one sterile filter is connected.
An apparatus of the this type is known, for example, from DE 34 44 671A.
Due to a so-called "dead-end" arrangement of the sterile filter in the substituate line, the above mentioned device has the drawback that in the course of time particles and other substances, e.g. imported germs and pyrogens, accumulate in front of the sterile filter membrane. This is especially dangerous if as a result of a rupture these substances can suddenly be carried into the sterile region, thereby contaminating the substitution fluid.
Further risks of contamination exist in the form of the substituate line and its additional components, such as, for example, substituate pump and ventilation means and, finally, the design of the substituate line itself is constructionally complex due to these added components, and thus very costly.
Further, it is known from the article by v. Albertini, et at., "Serial and parallel pairs of dialyzers for high-efficiency treatment", in Kidney International 31(1), 1987, page 247, to arrange serially or in parallel two blood filters to enhance the purifying action. A means for precisely regulating and monitoring the filtrate and substituate flow is not mentioned in this publication.
Operating these apparatuses both safely and efficiently requires costly and complex devices for regulating and monitoring the ratio of substituate and filtration. Moreover, measuring the permeability of the blood filter membrane is not possible without great expenditure and added structural complexity.
Thus, the object of the present invention is, based on a hemo(dia)filtration apparatus of the aforementioned kind, to provide a simpler, more efficient and safer hemo(dia)filtration apparatus, in which clogging of the sterile filter with germs or pyrogens is largely eliminated, in which the ratio of filtrate and substituate is regulated and monitored in a simple and safe manner, and in which the permeability of the blood filter membrane may be measured in a safe, simple manner.